Artemis's mother has contracted a deadly disease -- and the only cure lies in the brain fluid of African lemurs. Unfortunately, Artemis himself was responsible for making the lemurs extinct five years ago. Now he must enlist the aid of his fairy friends to travel back in time and save them. Not only that, but he must face his deadliest foe yet...his younger self.

Polly's stay with her grandparents in Connecticut becomes an extraordinary experience as she encounters old friends and mysterious strangers and finds herself traveling back in time to play a crucial role in a prehistoric confrontation.

Middle-school history teacher Rush Revere takes his students back in time to eighteenth-century Boston to experience the start of the American Revolution as it happens.

Dolphins at daybreak: Their magic tree house takes Jack and Annie deep into the sea, where they meet up with dolphins, sharks, and octopi as they search for the answer to an ancient riddle. Ghost town at sundown: Their magic tree house takes Jack and Annie back to the Wild West, where they experience excitement and danger and try to solve a riddle. Lions at lunchtime: The magic tree house takes Jack and Annie to Africa where they meet up with wonderful...

Jack and Annie travel 500 years back in time to Florence, Italy, and spend a day helping Leonardo da Vinci in the hope of learning another secret of happiness.